Apparatus and method for manufacturing a green tyre

ABSTRACT

The invention provides an assembly and a method for manufacturing a green tyre. The assembly comprises a building drum ( 52 ), an extrusion device ( 75 ) for extruding a strip ( 70 ) of an unvulcanized rubber, a transfer drum ( 72 ) for helically winding the strip ( 70 ) of the unvulcanized rubber thereon into a layer of rubber material, and a cutting device ( 76 ) for at least substantially in axial direction severing the layer of rubber material, wherein the transfer drum ( 72 ) is movable between a first position near the extrusion device ( 52 ) and a second position near the building drum ( 52 ) for transferring the layer of rubber material from the transfer drum ( 72 ) to the building drum ( 52 ).

BACKGROUND OF THE INVENTION

The present invention relates to an assembly and method for manufacturing an unvulcanized tyre or green tyre.

It is common practice to arrange various plies for a tyre, such as for instance a car tyre or truck tyre, on a building drum. Various plies of rubber, such as for instance the airtight liner, the sidewalls and the tread are combined with reinforcement plies, such as for instance carcass plies and breaker plies.

Applicant's European patent EP-B1-880436 describes an assembly for manufacturing a green tyre comprising a first device for manufacturing a breaker-tread package and a second device for manufacturing a carcass package. The assembly further comprises a transfer ring for moving the breaker-tread package from the first device to the second device to over the carcass package. Different layers in the breaker-tread package and the carcass package are supplied as a band of rubber material from a roll, wherein the band has a width that substantially corresponds with the width of the component in question in the green tyre, and wherein the strip is made to length that substantially corresponds with the circumferential length of the component in question in the green tyre. The band of rubber material is wound around the building drum wherein the adjacent outer ends of the bands are connected to one another by means of a splice. The breaker-tread package and the carcass package are stitched against each other by means of a stitcher for forming the green tyre.

Although the assembly according to European patent EP-B1-880436 as regards manufacturing different types of tyres is relatively flexible and has a high production capacity, switching from manufacturing tyres having one width to another width requires the changing of rolls of rubber bands.

A known alternative of the use of bands of rubber material is the so-called ‘strip winding’. Such a method and related device are for instance described in EP 1.827.807. The device is provided with an extrusion device that is adapted for extruding a thin strip of unvulcanized rubber, wherein the extruded strip is helically wound around the building drum for thus forming the desired layer of the rubber material. As the desired layer is in fact built up on the building drum by winding a thin strip, the dimensions of the desired layer can easily be adjusted by adjusting the winding process.

A drawback of ‘strip winding’ is that it generally takes more time to build up a desired layer by means of winding an extruded strip on a rotating building drum, than in one revolution of the building drum arranging a band of rubber material. Consequently, during the winding process the building drum is not available for quite some time for carrying out other method steps for manufacturing a green tyre.

It is an object of the invention to provide an assembly and a method for manufacturing a green tyre that uses a ‘strip winder’, wherein at least one of the drawbacks mentioned above is at least partially overcome.

SUMMARY OF THE INVENTION

According to a first aspect the invention for that purpose provides an assembly for manufacturing a green tyre, comprising

a building drum,

an extrusion device for extruding a strip of an unvulcanized rubber,

a transfer drum for helically winding the strip of the unvulcanized rubber thereon into a layer of rubber material, and

a cutting device for at least substantially in axial direction severing the layer of rubber material,

wherein the transfer drum is movable between a first position near the extrusion device and a second position near the building drum for transferring the layer of rubber material from the transfer drum to the building drum.

By using a transfer drum, on the one hand a layer of rubber material formed of strips by means of the extrusion device and having the desired dimensions can be built up on the transfer drum by adjusting the winding process, and on the other hand the layer of rubber material obtained can be arranged on the building drum substantially in one revolution. Preferably both the building drum and the transfer drum are rotatably positioned in the assembly, wherein the axes of rotation of the building drum and the transfer drum are placed substantially parallel, at least in the second position.

In the assembly according to the invention the desired layer of rubber material is built up by means of helically winding an extruded strip on the transfer drum. In that way the building drum will not be required during manufacturing the desired layer of rubber material and the building drum is available for carrying out other method steps for manufacturing a green tyre during manufacturing the desire layer.

In one embodiment the layer of rubber material is formed of several revolutions of the strip around the transfer drum. As winding the strip over several revolutions takes place around the transfer drum, the building drum can be kept free for carrying out other method steps for manufacturing a green tyre, during said winding process.

In one embodiment the transfer drum is axially movable during extruding. By slowly moving the transfer drum axially, the helically wound strips are arranged so as to be shifted with respect to each other in axial direction of the transfer drum, as a result of which the layer of rubber material can be built up.

The expert will understand that the effect mentioned above can also be achieved with an embodiment in which the extrusion device and the transfer drum are movable with respect to each other in the axial direction of the transfer drum.

In one embodiment a diameter of the transfer drum is at least substantially larger or equal to a diameter of the building drum. In that way a desired layer of rubber material having a length that suffices to enclose the building drum can be manufactured on the transfer drum. The layer of rubber material can thus be arranged on the building drum in one synchronised and at least substantially one continuous motion of the transfer drum and the building drum.

In an alternative embodiment the diameter of? the transfer drum is slightly smaller than the diameter of the building drum. As a result the sidewall will be arranged on the building drum in an advantageous manner with slight stretch.

In one embodiment the diameter of the transfer drum is variable. In that way the diameter of the transfer drum can be adjusted to another building drum diameter so that the layer of rubber material manufactured thereon after cutting to length corresponds with the circumference of the building drum.

In one embodiment for building up a tyre component, such as for instance a sidewall or a tread, in some cases two, three or more extrusion devices can also be used, wherein the various extrusion devices preferably are adapted for extruding rubber components of different compositions.

In one embodiment the transfer drum is provided with a cooling device for cooling down the rubber material on the transfer drum. When extruding the strip of unvulcanized rubber material the rubber material is usually heated. After extrusion and winding the strip of rubber material, the rubber material will cool down as a result of which the rubber material will shrink. In the known devices wherein the extruded material is arranged directly on the building drum, the material will cool down during winding onto the building drum and/or after it has been arranged on the building drum. The shrinkage this entails changes the dimensions of the extruded material on the building drum. This problem is at least partially overcome with the transfer drum including cooling device because the extruded material on the transfer drum can be forcedly cooled down, and in an at least partially cooled down condition is transferred from the transfer drum to the building drum. In that way less shrinkage will occur at transferring the layer of rubber material from the transfer drum to the building drum, which results in improved dimensional stability of the layer of rubber material at transferring.

In one embodiment the cooling device comprises one or several pipes for passing a cooling medium through them, for instance a cooling gas or a coolant, wherein the one or several pipes are placed near a circumferential wall of the transfer drum, particularly for discharging heat from the circumferential wall of the transfer drum.

In one embodiment the cooling device comprises one or several Peltier elements, wherein the one or several Peltier elements are placed near a circumferential wall of the transfer drum, particularly for discharging heat from the circumferential wall of the transfer drum.

In one embodiment the transfer drum comprises a cutting zone where the cutting device is able to sever the layer of rubber material, wherein the transfer drum, at least near the cutting zone, comprises a retaining device for retaining the layer of rubber material. The retaining device ensures that the layer of rubber material even after cutting remains sitting correctly on the transfer drum and can be transferred correctly from the transfer drum to the building drum.

In a simple embodiment the retaining device comprises a vacuum source that is in flow connection with a number of suction nozzles that debouch at least near the cutting zone. By using suction nozzles one the one hand the layer of rubber material can be retained on the transfer drum, and on the other hand the layer of rubber material can be pushed free from the transfer drum, for instance by blowing off compressed air via the suction nozzles. Said pushing free can be used during transferring the layer of rubber material from the transfer drum to the building drum.

In one embodiment the transfer drum comprises a cutting zone where the cutting device is able to sever the layer of rubber material, wherein the transfer drum, at least in or near the cutting zone, comprises a separation member for keeping the outer ends of the layer, formed by severing the layer of rubber material, spaced apart from one another during transferring the layer of rubber material from the transfer drum to the building drum. During transferring the layer of rubber material from the transfer drum to the building drum the transfer drum is placed against the building drum with the layer of rubber material in between, such that at least one of the outer ends is pressed against the building drum. The separation member substantially prevents that during said pressing down the at least one outer end will adhere again to the other outer end which may disrupt transferring the layer of rubber material.

In one embodiment the separation member is adapted for keeping the outer ends spaced apart substantially in radial direction of the transfer drum, during transferring the layer of rubber material from the transfer drum to the building drum. The radially most outwardly situated outer end will be the first to be pressed against the building drum and the transfer drum and the building drum are rotated substantially synchronously for transferring the rest of the layer of rubber material on the building drum.

In one embodiment the separation member comprises a surface part of the transfer drum that is rotatably connected to a circumferential surface of the transfer drum, wherein the axis of rotation is situated near or in the circumferential surface of the transfer drum. Advantageously the cutting device will sever the layer of rubber material along a line situated near or along a side of the circumferential part extending away from the axis of rotation. By rotating the surface part over a small angle the outer ends of the layer formed by severing the layer of rubber material can be placed spaced apart from one another substantially in radial direction of the transfer drum.

The assembly according to the invention is particularly suitable for arranging on the building drum a rubber layer that is not fibre-reinforced or not cord-reinforced, such as for instance one or several tread plies or a sidewall. It is noted that one or several tread plies are usually placed on a breaker ply that was already placed previously on the building drum, and the side wall is usually placed on a carcass ply including body ply that was already placed previously on the building drum. In addition it is also possible to arrange the sidewalls as first component on the building drum.

According to a further aspect the invention provides a method for manufacturing a green tyre, comprising the steps of:

from an extrusion device extruding a strip of an unvulcanized rubber material;

during extruding helically winding the strip on a transfer drum for forming a layer of rubber material;

at least substantially in axial direction severing the layer of rubber material; and

transferring the cut layer of rubber material from the transfer drum onto a building drum by means of substantially simultaneously unwinding the layer from the transfer drum and winding up the layer onto the building drum.

In one embodiment the strip is wound into the layer of rubber material over several revolutions of the transfer drum.

In one embodiment the transfer drum rotates and is axially moved during extruding.

In one embodiment the extrusion device and the transfer drum are moved with respect to each other in axial direction of the transfer drum during extruding.

In one embodiment the layer of rubber material is arranged on the building drum substantially in one revolution thereof, preferably by means of a substantially continuous rotation of the building drum.

In one embodiment the layer of rubber material is formed using two, three or more extrusion devices, wherein the various extrusion devices extrude rubber components of different compositions.

In one embodiment the transfer drum is movable between a first position near the extrusion device and a second position near the building drum for transferring the layer of rubber material from the transfer drum to the building drum.

In one embodiment the transfer drum is rotatable about a first axis of rotation and the building drum is rotatable about a second axis of rotation, wherein the first and the second axis of rotation are placed substantially parallel, at least during transferring the cut layer.

In one embodiment the rubber material on the transfer drum is forcedly cooled, preferably by means of a cooling device in the transfer drum.

In one embodiment the rubber material, at least near a cutting zone thereof where the cutting device is able to sever the layer, is retained on the transfer drum by means of a retaining device, wherein the retaining device preferably is a part of the transfer drum.

In one embodiment after cutting the layer of rubber material and during transferring the layer of rubber material from the transfer drum to the building drum the outer ends of the layer formed by cutting are kept spaced apart from one another by means of a separation member.

In one embodiment during transferring the layer of rubber material from the transfer drum to the building drum, the separation member keeps the outer ends spaced apart substantially in radial direction of the transfer drum.

The aspects and measures described in this description and the claims of the application and/or shown in the drawings of this application may where possible also be used individually. Said individual aspects may be the subject of divisional patent applications relating thereto. This particularly applies to the measures and aspects that are described per se in the sub claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of a number of exemplary embodiments shown in the attached drawings, in which:

FIG. 1 shows a schematic view of an exemplary embodiment of an assembly according to the invention;

FIG. 2 shows a schematic side view of an exemplary embodiment of a device for ‘strip winding’ using a transfer drum;

FIGS. 3A-3G show the device of FIG. 2 during various steps for manufacturing a layer of rubber material on a transfer drum and transferring it onto a building drum;

FIGS. 4A and 4B show details of the steps for transferring the layer of rubber material from the transfer drum to the building drum; and

FIG. 5 shows a schematic view of a second exemplary embodiment of an assembly according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic top view of an exemplary embodiment of an assembly according to the invention. The inventive assembly 1 comprises a first machine case 11 that is placed so as to be movable on a transport rail 21. The first machine case 11 bears a building drum, particularly a breaker-tread building drum 12. The breaker-tread building drum 12 is rotatably connected to the first machine case 11, wherein the first machine case 11 comprises a drive, preferably servo-controlled, for driving a rotation of the breaker-tread drum 12 about an axis of rotation extending substantially horizontally and substantially parallel to the transport rail 21.

In a known manner the breaker-tread drum 12 comprises an internal mechanism that is able to have for instance 24 magnet segments at the outside of the drum assume a smaller diameter, for removing the breaker or breaker components and tread components, or assume a larger diameter, respectively, for arranging breaker and tread components. If the breaker does not need to contain steel cords, instead of a building drum with magnets, a known air vacuum operated building drum can be used.

The inventive assembly also comprises a breaker ply servicer 31 for cut to length supplying breaker plies 32, 33 to the breaker-tread building drum 12. By means of this breaker ply servicer 31, a first breaker ply 32 and a second breaker ply 33, the cord direction of which is opposite the cord direction of the first breaker ply 32, are successively wound around the building drum 12.

The breaker ply servicer 31 comprises a conveyor with a support surface for producing the breaker plies 32, 33 thereon. The conveyor is able to move the breaker plies 32, 33 in a conveyance direction T for supplying the breaker plies 32, 33 to the breaker-tread building drum 12.

After both having been produced, the breaker plies 32, 33 are wound on the breaker-tread building drum 12. As the first breaker ply 32 has been placed downstream of the second breaker ply 33, the first breaker ply 32 is the first to be placed on the building drum 12 and after that the second breaker ply 33 is placed on the first breaker ply 32, wherein a breaker ply package is formed wherein the rubber strips are placed in between the first and second breaker ply.

The inventive assembly furthermore comprises a transport rail 21, which, considered in vertical direction, is placed below the building drum 12. The machine case 11 is movable along the transport rail 21. When the breaker ply package has been placed on the building drum 12 the machine case 11 is moved along the transport rail 21 to the tread winding device 40. In addition the machine case 11 preferably also is substantially vertically movable, so that the breaker-tread building drum 12 borne by the machine case is movable in a direction substantially perpendicular to the transport rail 21 and thus can easily be moved towards the cut to length breaker plies 32, 33 of the breaker ply servicer 31, in order to pick them up.

The tread winding device 40 comprises a first extrusion device 41 for extruding a strip of rubber material directly on the breaker ply package. The building drum 12 is then moved along the extrusion device along the transport rail 21 while the building drum 12 rotates as a result of which the strip is wound on the breaker ply package. This known method is also called ‘strip winding’, and the extrusion device 41 is adapted for arranging a tread basic ply on the breaker ply package.

The tread winding device 40 comprises a second extrusion device 42 for extruding a strip of rubber material directly on the tread basic ply for forming a tread cover ply. In this case as well the building drum 12 is moved along the extrusion device along the transport rail 21 while the building drum 12 rotates as a result of which the strip is wound on the tread basic ply.

If the machine case 11 is also substantially vertically movable, the breaker-tread building drum can very easily be moved in the direction of the first extrusion device 41 and/or second extrusion device 42 for picking up the tread basic ply and/or tread cover ply, respectively, therefrom.

The breaker-tread package will be substantially complete after this, and this package is taken from the breaker-tread building drum 12 by a transfer ring 22 that is movably placed on the transport rail 21. The transfer ring 22 with the breaker-tread package is moved to an attending position and the next tread-breaker package can be assembled on the breaker-tread building drum 12.

The assembly 1 according to the invention furthermore comprises a second machine case 51 that is substantially fixedly positioned. A rotatable carcass drum 52 is placed on a side of the second machine case 51 facing the transport rail 21. The carcass drum 52 is rotatably connected to the second machine case 51, wherein the second machine case 51 comprises a drive, preferably servo-controlled, for driving a rotation of the carcass drum 52 about a substantially horizontally extending axis of rotation.

Rubber sides are placed on the carcass drum 52. The rubber sides are manufactured by means of ‘strip winding’ on a transfer drum. For that purpose the assembly 1 is provided with two transfer drums 71, 72 that are movable along a second transport rail 73. The assembly 1 further comprises a first extrusion device 74 for extruding a strip of an unvulcanized rubber material, wherein the during extruding the strip is wound on a first transfer drum 71 into a layer of rubber material for forming a first rubber sidewall, and a second extrusion device 75 for extruding a strip of an unvulcanized rubber material, wherein the strip during extruding is wound on a second transfer drum 72 into a layer of rubber material for forming a second rubber sidewall.

As described below in more detail the first and second rubber sidewalls are severed at least substantially in axial direction of the transfer drums 71, 72, and the cut sidewalls are transferred from the transfer drums 71, 72 onto the carcass drum 52 by means of substantially simultaneously unwinding the layer from the transfer drum 71, 72 and winding up the layer onto the carcass drum 52.

Furthermore from an inner liner manufacturing device 62 and a carcass material manufacturing device 61 an airtight inner liner and the carcass components are successively placed on a carcass inner liner transport device 63. By means of a carcass inner liner arrangement device 64 the airtight inner liner and the carcass components can be placed on the carcass drum 52.

From a bead wire bundle servicer 65 bead wire bundles with filling strip are transferred on a bead holding and bead positioning apparatus 66 that is movable over the transport rail 21. Said apparatus 66 is slid over the carcass drum 52, on which the carcass components have already been arranged, and the bead wire bundles with filling strips are placed on the carcass drum 52, after which by operating the carcass drum 52 the bead wire bundles with filling strips are pressed down onto the carcass ply and an airtight closure is formed.

Depending on the type of carcass drum used the carcass plies and rubber sidewalls are turned up differently around the bead wire bundles with filling strip. In case of a so-called “dual bladder” carcass drum this takes place using four bladders. For turning up the carcass plies and the rubber sidewalls around the bead wire bundles, the carcass drum can also be provided with two series of turn-up arms, wherein each series comprises several swinging turn-up arms placed distributed over the circumference of the carcass drum 52.

When the carcass is completed, in this case for a tread-over-sidewall structure, the transfer ring 22 with breaker-tread package is moved from the attending position to over the carcass drum 52 and the breaker-tread package needs to be stitched against the carcass components by a stitcher for forming a green tyre.

The completed green tyre is taken from the carcass drum 52 by the transfer ring 22 and transported to near the removal apparatus 23 which takes the green tyre from the transfer ring 22. After that the transfer ring 22 is moved towards the breaker-tread building drum 12 for removing the next breaker-tread package.

The assembly 1 is furthermore provided with a robot 24 for supplying the bead wire bundles and for removing the manufactured green tyres.

The assembly 1 turns out to be highly flexible, both as regards the types of tyre to be manufactured and, due to the modular structure of the assembly 1, the exchangeability of the individual devices that constitute the assembly.

One of the devices constituting the assembly 1 is the device for manufacturing the rubber sidewalls. FIG. 2 shows a schematic side view of said device that is placed near the carcass drum 52.

The device comprises an extrusion device 75 for extruding a strip 70 of an unvulcanized rubber. Prior to the extrusion, the circumferential surface of the transfer drum 72, placed on a transport device 77, is placed near the extrusion device 75 as shown in FIG. 3A. During its extrusion, the strip 70 is wound on the rotating transfer drum 72 as shown in FIG. 3B. In order to retain the beginning of the strip 70 on the transfer drum 72, it is provided with a retaining device 79, for instance in the form of a number of suction nozzles which debouch at least at the circumferential surface of the transfer drum 72 and which are in flow connection with a vacuum source.

Preferably the transfer drum 72 is provided with a cooling device for discharging heat required for the extrusion.

As during extruding the transfer drum 72 rotates and is slowly moved axially, the strip 70 is wound substantially helically around the transfer drum 72 for forming a layer of rubber material. The layer of rubber material is thus formed of several revolutions of the strip 70 around the transfer drum 72.

After the layer of rubber material 70 has been completed, the transfer drum 72 is moved away from the extrusion device 75 as shown in FIG. 3C.

Subsequently the layer of rubber material 70 is severed at least substantially in axial direction of the transfer drum 72 using a cutting device 76, for instance an ultrasonic knife, as shown in FIG. 3D. Preferably the layer of rubber material is not cut in radial direction of the transfer drum but at an angle of 18 degrees to the circumferential surface of the transfer drum. The layer 70 thus acquires a sharp tip ensuring that deviations in the splice overlap are ‘evened out’. Cutting radially would result in a 90-degree cut, which is not desirable. That is why the cutting device 76 is placed at a distance above a centre line. In that way the cut is made at an angle.

An additional advantage is that the motion available to the drum anyway can also be used for the cutting process. In this application a cutting angle of between 18 and 30 degrees can be obtained.

Subsequently the transfer drum 72 is moved by the transport device 77 between a first position near the extrusion device 75 and a second position near the carcass drum 52 for transferring the layer of rubber material 70 from the transfer drum 72 to the building drum 52 as shown in FIGS. 3F and 3G.

As shown in the figures the diameter of the transfer drum 72 is at least substantially equal to the diameter of the carcass drum 52. As a result the layer of rubber material 70 can be arranged on the carcass drum or building drum 52 in substantially one revolution thereof, preferably by means of a substantially continuous rotation of the carcass drum.

It will furthermore be clear that the transfer drum 72 is rotatable about a first axis of rotation and that the carcass drum 52 is rotatable about a second axis of rotation, wherein the first and the second axis of rotation are placed substantially parallel, at least during transferring the cut layer 70 as shown in the FIGS. 3F and 3G.

The transfer drum 72, at least near a cutting zone 79 thereof where the cutting device 76 is able to sever the layer 70, is provided with a separation member 80. The separation member 80 comprises a surface part 81 of the transfer drum 72 that is rotatably connected to a circumferential surface of the transfer drum 72, wherein the axis of rotation 78 is situated near or in the circumferential surface of the transfer drum 72. By at least partially folding the surface part 81 inwards the outer ends of the layer formed by severing the layer of rubber material 70 can be placed at a distance d from one another. In that case the distance d extends substantially in radial direction from the transfer drum 72 as shown in FIG. 3E.

FIG. 4A shows the separation member 80 in detail during the step according to FIG. 3F. In this situation the cutting device 76 severs the layer of rubber material 70 along a line situated near or along a side of the surface part 81 extending away from the axis of rotation 78. By rotating the surface part 81 over a small angle the outer ends 83, 84 of the layer 70 formed by severing the layer of rubber material 70 can be placed substantially in radial direction of the transfer drum 72 at a distance d from one another. It is noted here that the distance d is shown in a highly exaggerated manner in the figures for the sake of clarity.

FIG. 4B show the separation member 80 in detail during the step according to FIG. 3G. During transferring the layer of rubber material 70 from the transfer drum 72 to the carcass drum 52, the transfer drum 72 is placed against the carcass drum 52 with the layer of rubber material 70 in between. In that case the radially most outwardly situated outer end 83 of the layer of rubber material 70 is the first to be pressed against the carcass drum 52 and according to the step as shown in FIG. 3G the transfer drum 72 and the carcass drum 52 are substantially synchronously rotated for transferring the rest of the layer of rubber material 70 onto the carcass drum 52. The separation member 80 is able to prevent that during pressing down, the outer ends 83, 84 of the layer of rubber material 70 adhere again.

Finally FIG. 5 shows a second embodiment of an assembly 1′, wherein the tread-winding device 40′ comprises a transfer drum 43 that can be moved along a transport rail 44, and wherein the extrusion devices 41, 42 extrude the strip of rubber material first on the transfer drum in the same manner as discussed above with reference to FIGS. 3A-3G.

Summarizing the invention provides an assembly and a method for manufacturing a green tyre. The assembly comprises a building drum, an extrusion device for extruding a strip of an unvulcanized rubber, a transfer drum for helically winding the strip of the unvulcanized rubber thereon into a layer of rubber material, and a cutting device for severing the layer of rubber material, wherein the transfer drum is movable between a first position near the extrusion device and a second position near the building drum for transferring the layer of rubber material from the transfer drum to the building drum.

The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert. 

1-25. (canceled)
 26. Method for manufacturing a green tyre, comprising the steps of: from an extrusion device extruding a strip of an unvulcanized rubber material; during extruding helically winding the strip on a transfer drum for forming a layer of rubber material; at least substantially in axial direction severing the layer of rubber material; and transferring the cut layer of rubber material from the transfer drum onto a building drum by means of substantially simultaneously unwinding the layer from the transfer drum and winding up the layer onto the building drum.
 27. Method according to claim 26, wherein the strip is wound into the layer of rubber material over several revolutions of the transfer drum.
 28. Method according to claim 26, wherein the extrusion device and the transfer drum are moved with respect to each other in axial direction of the transfer drum during extruding.
 29. Method according to claim 26, wherein the layer of rubber material is arranged on the building drum substantially in one revolution thereof.
 30. Method according to claim 29, wherein the layer of rubber material is arranged on the building drum by means of a substantially continuous rotation of the building drum.
 31. Method according to claim 26, wherein the layer of rubber material is formed using two, three or more extrusion devices, wherein the various extrusion devices extrude rubber components of different compositions.
 32. Method according to claim 26, wherein the transfer drum is movable between a first position near the extrusion device and a second position near the building drum for transferring the layer of rubber material from the transfer drum to the building drum.
 33. Method according to claim 26, wherein the transfer drum is rotatable about a first axis of rotation and the building drum is rotatable about a second axis of rotation, wherein the first and the second axis of rotation are placed substantially parallel, at least during transferring the cut layer.
 34. Method according to claim 26, wherein the rubber material on the transfer drum is forcedly cooled by means of a cooling device in the transfer drum.
 35. Method according to claim 26, wherein the rubber material, at least near a cutting zone thereof where the cutting device is able to sever the layer, is retained on the transfer drum by means of a retaining device, wherein the retaining device is a part of the transfer drum.
 36. Method according to claim 26, wherein after cutting the layer of rubber material and during transferring the layer of rubber material from the transfer drum to the building drum the outer ends of the layer formed by cutting are kept spaced apart from one another by means of a separation member, wherein during transferring the layer of rubber material from the transfer drum to the building drum, the separation member keeps the outer ends spaced apart substantially in radial direction of the transfer drum.
 37. Assembly for manufacturing a green tyre, comprising a building drum, an extrusion device for extruding a strip of an unvulcanized rubber, a transfer drum which is arranged for helically winding the strip of the unvulcanized rubber thereon into a layer of rubber material, and a cutting device for at least substantially in axial direction severing the layer of rubber material, wherein the transfer drum is movable between a first position near the extrusion device and a second position near the building drum for transferring the layer of rubber material from the transfer drum to the building drum.
 38. Assembly according to claim 37, wherein the layer of rubber material is formed of several revolutions of the strip around the transfer drum.
 39. Assembly according to claim 37, wherein the diameter of the transfer drum is at least substantially larger or equal to the diameter of the building drum.
 40. Assembly according to claim 37, wherein the diameter of the transfer drum is variable.
 41. Assembly according to claim 37, provided with two, three or more extrusion devices adapted for extruding rubber components of different compositions.
 42. Assembly according to claim 37, wherein the transfer drum is provided with a cooling device for cooling down the rubber material on the transfer drum.
 43. Assembly according to claim 37, wherein the transfer drum, at least near a cutting zone thereof where the cutting device is able to sever the layer, comprises a retaining device for retaining the layer of rubber material.
 44. Assembly according to claim 37, wherein the transfer drum, at least near a cutting zone thereof where the cutting device is able to sever the layer, comprises a separation member for keeping the outer ends of the layer, formed by severing the layer of rubber material, spaced apart from one another during transferring the layer of rubber material from the transfer drum to the building drum.
 45. Assembly according to claim 44, wherein the separation member is adapted for keeping the outer ends spaced apart substantially in radial direction of the transfer drum, during transferring the layer of rubber material from the transfer drum to the building drum, wherein the separation member comprises a surface part of the transfer drum wherein the surface part is rotatably connected to a circumferential surface of the transfer drum, wherein the axis of rotation is situated near or in the circumferential surface of the transfer drum. 